1. Field of the Invention
The present invention relates to an apparatus for bending glass sheets conveyed along a horizontal path from a furnace, either between upper and lower molds or under gravitational forces, and a method of bending glass sheets by employing such an apparatus.
2. Description of the Relevant Art
Various method and apparatus for producing bent glass sheets for use in vehicles such as automobiles or the like have been proposed in the art. U.S. Pat. No. 3,595,636 to Posney discloses a glass sheet bending apparatus for pressing and then quenching a glass sheet conveyed vertically from a furnace between vertical molds. U.S. Pat. Nos. 3,529,947 and 3,573,022 to Frank disclose apparatus for pressing and quenching a glass sheet conveyed horizontally from a furnace, between upper and lower molds. U.S. Pat. Nos. 3,476,540 and 3,554,724 to Ritter, Jr., et al reveal glass sheet bending apparatus in which when a heat softened glass sheet is deposited on conveyor rolls in the bending apparatus, a ring-type lower mold member is moved upwardly to cause the glass sheet to sag into conformity with the shaping surface of the lower mold member under inertial and gravitational forces on the glass sheet. U.S. Pat. Nos. 4,197,108 and 4,272,274 to Frank et al show apparatus in which a lower shaping mold composed of a solid block having a plurality of elongated shaping memers with smooth upper concave surfaces is lifted from below conveyor rolls to cause the glass sheet to sag into a bent shape on the lower shaping mold under gravitational forces. Similarly, U.S. Pat. No. 3,454,389 to O'Connell et al shows apparatus in which a lower shaping mold composed of a plurality of spaced, elongated shaping members with smooth upper concave surfaces is lifted from below conveyor rolls to cause the glass sheet to sag into a bent shape on the lower shaping mold under gravitational and inertial forces. U.S. Pat. No. 3,734,706 Ritter, Jr. disclosed an apparatus having a ring-type lower mold movable upwardly from below conveyor rolls to bend a glass sheet on the lower mold under inertial and gravitational forces, the bent glass sheet being rapidly chilled.
In such conventional apparatus, or discussed above, in which the glass sheet is raised off the conveyor rolls by the ring-type lower mold, the glass sheet sags or flexes in its central area under inertial forces created as it is lifted against the mass of air present over the upper surface of the glass sheet, and under the gravitational forces acting on the mass of the glass sheet. The central area of the glass sheet having the inertial-induced sag remains in contact with the conveyor rolls for a prolonged period of time. Those portions of the glass sheet which are kept in contact with the conveyor rolls are cooled more rapidly than the other glass sheet portions, and are subject to optical defects. The other conventional apparatus discussed above wherein the lower mold, in the form of a solid block having a shaping surface conforming substantially to the entire surface of a glass sheet, is raised to lift the glass sheet off the conveyor rolls are disadvantageous in that if the heated and softened glass sheet were deposited on the shaping surface immediately over virtually the entire surface of the glass sheet, then the important central area of the glass sheet would be liable to have optical defects.
The present invention has been made in an effort to eliminate the problems and disadvantages of the conventional apparatus.